1. Field of the Invention
This invention relates to a method and an apparatus for removing flash of polymeric molded products.
2. Description of the Related Art
In the art of injecting synthetic polymers into dies to make molded products, the molded products taken away from the dies, in general, unfavorably have flash. Since the dies are assembled to give the die matching surface, the polymers may enter into the die matching surface and solidified there to make flash.
Furthermore, there are specific methods even positively allowing the flash to be produced. For example, in the case of molding foam polyurethane products, the gap at the die matching surface may be slightly enlarged to allow air in the dies to easily escape through the gap.
Referring to FIGS. 27 and 28 showing the related art, a mandrel 202 is located in insert dies (not shown); foam polyurethane is injected into the dies; the solidified polymeric molded product is taken away from the dies to obtain a steering wheel 205 (called simply "ring" hereafter) the mandrel 202 of which is covered with armoring material 201.
During the molding, burr 203 is produced at the inner and outer peripheries of the ring 205. Furthermore, since the molten polymer is injected into the dies generally through a polymer injection path called gate, the ring 205 is provided with a solidified polymeric substance 204 set in the injection path (called solidified gate hereafter) as the dies are cooled.
Since the burr 203 is useless for the ring 205, it is usually cut and removed from the ring 205. Of course, the solidified gate 204 is also removed.
Heretofore, the burr removing operation for the burr 203 has been carried out by a manual work using a cutter.
However, the burr removing operation by the manual work has the following problems: the removal leaves uneven trace; a part of product other than the burr would often be removed to make inferior goods; and the work efficiency is poor.
Under the circumstances, a motor-driving flash removing operation may be considered in which a cutter is installed on the rotary shaft of a motor; the motor is operated by a robot; and the cutter is applied to the flash of the polymeric molded product to remove it.
The direct performance of this motor-driving method can cut and remove the flash, but it suffers from the following problems: excessive removal would occur to remove a part of product other than the burr; or insufficient removal would occur to leave a part of the flash, lowering the commercial value of the products.
Furthermore, soft polymeric molded products and foam products such as polyurethane and rubber, in practice, have at their outer surfaces undulation within tolerance because of their molding distortion. In this case, the above problems would become more remarkable unless the cutter is moved to follow the undulation.
Accordingly, the burr removing operation by the mechanical means having the function of simple cutter rotation has not been in practical use.
On the other hand, using the usual reamer would be considered for the flash removing operation.
The reamer used for this flash removing operation is, as shown in FIG. 29, the very same reamer 206 for metallic materials. Using this reamer 206, its blades 207 often invade a part of product unless careful operation is performed, to make inferior goods. Thus, this operation requires high skill and great care.
Furthermore, the reamer 206 defines grooves 208 of V-shape cross sections between the blades 207; the bottom of the groove 208 is provided with a crack-preventing groove 209 of circular cross section. The removed flash is easy to be collected in the grooves 209, so that some cases require another operation of taking away the collected flash from the grooves 209.
In addition to the above problems, the flash removing operation by the mechanical means would suffer from another problem that works to be processed such as polymeric molded products have to be supported and fixed by appropriate different jigs for different works.
Namely, the works tend to have much variety in shapes because of the use of the small-amount multiproduct production system in recent years, so that it shows a tendency to increase that the works of the same kind have different shapes in detailed structures among them. Therefore, in processing the works, jigs have to be replaced by other ones for different works having different detailed structures.
Such replacement of jigs would cause replacement of associated devices, for example cutting tools, requiring much labor. Using wrong cutting tools, inferior goods would be produced.